High Surf Warning 7, NWS Honolulu, HI

832 
WHHW40 PHFO 101341
CFWHFO

Coastal Hazard Message
National Weather Service Honolulu HI
341 AM HST Tue Apr 10 2018

...HIGH SURF ADVISORY FOR NORTH AND WEST FACING SHORES OF NIIHAU 
KAUAI OAHU AND MOLOKAI AND NORTH FACING SHORES OF MAUI...

.A large northwest swell that peaked above predicted levels overnight
has begun to ease early this morning. Surf along north and west 
facing shores will hold at advisory levels today, then drop below 
tonight. 

HIZ001>003-006>009-012-013-017-020-110245-
/O.CAN.PHFO.SU.W.0007.000000T0000Z-180410T1600Z/
/O.NEW.PHFO.SU.Y.0022.180410T1341Z-180411T0400Z/
Niihau-Kauai Windward-Kauai Leeward-Waianae Coast-
Oahu North Shore-Oahu Koolau-Olomana-Molokai Windward-
Molokai Leeward-Maui Windward West-Windward Haleakala-
341 AM HST Tue Apr 10 2018

...HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST THIS EVENING...
...HIGH SURF WARNING IS CANCELLED...

The National Weather Service in Honolulu has issued a High Surf
Advisory, which is in effect until 6 PM HST this evening. The
High Surf Warning has been cancelled. 

* SURF...Along north and west facing shores of Niihau and Kauai,
  and north facing shores of Oahu, Molokai, and Maui, 16 to 22
  feet. Along west facing shores of Oahu and Molokai, 10 to 15 
  feet. 

* TIMING...through this afternoon.

* IMPACTS...Moderate...Expect strong breaking waves, shore break,
  and strong longshore and rip currents making swimming difficult
  and dangerous.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Beachgoers, swimmers, and surfers should heed all advice given by
ocean safety officials and exercise caution. 

&&

$$

Gibbs

Area Forecast Discussion
National Weather Service Honolulu HI
403 PM HST Mon Apr 9 2018

.SYNOPSIS...
Unsettled weather will persist over the Big Island this evening
due to a departing upper level trough. Breezy trade winds and
more stable weather will spread south across all islands later
tonight. A weak midlevel disturbance will move eastward across
the islands Wednesday through the rest of the work week resulting
in a relatively wet trade wind weather pattern.

&&

.DISCUSSION...
A positively-tilted upper level trough over the Big Island is
producing a cloudy skies and a few thunderstorms over the
interior and leeward slopes this afternoon. We anticipate the
unsettled weather to continue across the Big Island through the
evening. The 00Z Hilo sounding indicates precipitable water value
of 1.76 inches, a weak midlevel inversion with decent CAPE above
10 kft. Satellite shows layered clouds across the entire Big
Island due to mid and high clouds associated with the trough,
along with low level clouds along a shear line axis. As the upper
trough will exit east of the area tonight, we have cancelled the
Flash Flood Warning that was in effect for the Big Island.
However, a slight chance of thunderstorms is in the forecast for
the evening across the Big Island.

A more stable airmass, along with breezy trade winds, moved over the
western half of the state last night and this morning, and should
reach the Big Island later tonight. The trade winds are driven by
a surface high pressure system currently northwest of the state.
As the high tracks eastward over the next couple of days, trade
winds will strengthen. Lingering low clouds and showers carried
by the northeasterly trade winds will affect mountains and
windward slopes, through rainfall amounts will be relatively light
over the smaller islands. A few passing showers may reach leeward
slopes.

Low clouds and showers will continue to track over the windward
slopes of Maui and the Big Island Tuesday and Wednesday due to
a weakening shear line near the Big Island. However, the
atmospheric stability will return, so rain intensity should drop
off. In short, it will be a wet trade wind pattern for Maui and
the Big Island, and typical/dryer trade wind weather for the
remaining islands for the next couple of days.

A weak midlevel disturbance may pass through the trade wind flow
around Wednesday and provide an uptick in trade wind showers
during the second half of the week for all islands. The trades
will focus more of the showers over windward and mauka areas.
Winds will also ease a bit on Thursday as the trade wind- driving
high pressure shifts far northeast of the area. Another strong
high pressure passing far north of the islands will again
strengthen the trade winds through this weekend.

&&

.AVIATION...
Strengthening high pressure to the northwest of the state will
encourage breezy trade wind flow statewide. Low cloud and
showers, the remnants of a shear line, are expected to linger
across the eastern half of the state into Tuesday.

Widespread MVFR CIG and VIS expected across windward
areas of Maui and the Big Island with Isolated IFR conditions
possible at times in locally heavy downpours. Prevailingly VFR
conditions expected across the remainder of the with only isolated
MVFR conditions in passing showers.

AIRMETs for mountain obscuration remain in effect for Maui
Molokai Lanai and Windward Big Island, but have expired for Oahu
and Kauai. Conditions are expected to persist overnight and
possibly spread to Leeward Big Island tonight.

&&

.MARINE...
The threat for heavy showers or thunderstorms over the coastal
waters surrounding the Big Island continues through this evening.

Breezy north to northeast winds have spread in over the coastal
waters from the north, with locally strong winds channeling
between the islands from Alenuihaha Channel northward, resulting
in conditions that are dangerous to small craft. Moderate winds
will remain south of the Big Island.

The incoming northwest swell has already brought a rise in seas
to exposed north and northwest waters this afternoon, and those
areas have been factored in to the expansion of the SCA mentioned
above. This swell is bringing increasing surf to the north and
west facing shores this afternoon with a peak expected tonight.
The swell will then trend down Tuesday and Wednesday. A High Surf
Advisory is posted for the exposed north and west facing shores
through Tuesday afternoon.

Another smaller sized northwest swell is possible Thursday, which
will then become reinforced by a larger northwest swell on
Friday into the weekend. Choppy surf along east facing shores
will be on the rise this week as trade winds increase.

See the latest Oahu Surf Discussion (SRDHFO) for additional
details on surf and swell.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST Tuesday for north and west
facing shores of Niihau, Kauai, Oahu, Molokai and Maui.

Small Craft Advisory until 6 PM HST Tuesday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Kaiwi Channel-Maui County Windward Waters-
Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island
Windward Waters.

&&

DISCUSSION...Foster
AVIATION...Bedal
MARINE...Brenchley